This application claims the priority of German application 199 16 692.2, filed in Germany on Apr. 14, 1999, the disclosure of which is expressly incorporated by reference herein.
When threads or yarns are wound onto bobbins, for example in open-end spinning machines, the respective thread is moved to and fro tranversely to its running direction. This to and fro motion of the thread is called traversing. A characteristic measure for the transverse speed is the double stroke count, that is one motion forward, one motion back.
In winding devices, in which the bobbin is driven by a friction roller at its periphery, a so-called random crosswinding occurs. In the production of such random crosswindings, there is the risk that from time to time so-called patterns or surfaces occur. Such patterns or surfaces arise then when per double stroke of the yarn guide of the traversing device, complete bobbin revolutions take place.
In the area of these patterns or surfaces, a plurality of wound layers are disposed directly one over the other, whereby the bobbin obtains a rib-like appearance. Such patterns or surfaces later impair the running off properties of the bobbin, in that they lead to end breaks or possibly to a defective bobbin. Such patterns or surfaces can also lead to an erratic placement of the bobbin on its friction roller and thus to possible damage of the bobbin.
It is known to effect an antipatterning in that the double stroke count is constantly changed periodically or aperiodically within a predetermined narrow time limit. In the case of automatic winding machines with a single drive for each bobbin, the antipatterning can be applied exactly then when the risk of a pattern directly threatens. When the bobbins, as is the case in open-end spinning machines, are driven centrally by a winding shaft extending in machine longitudinal direction, it must be considered that the fullness of each individual bobbin differs greatly from winding station to winding station. This is overcome in that the antipatterning is applied even when it is not necessary. This occurs by means of continuous so-called wobbling, whereby the speed of the winding shaft and/or the traversing speed of the yarn guide rod are constantly varied, i.e. the actual constant nominal speed of the winding shaft and/or the traversing speed is overriden by a periodic, for example, sinusoidal interference function, the so-called wobble curve.
In a known device in German published patent application 43 37 891, on which the present invention is based, the individual threads are fed to the bobbins from a delivery device with constant delivery speed. A winding shaft serves as a drive for the bobbins, on which shaft is arranged a plurality of friction rollers, on which the individual bobbins are disposed and driven on their peripheries. A traverse gearing serves to provide the traverse motion of the yarn guiding rod. A plurality of yarn guides, placed at the bobbins and moving to and fro, are arranged on the yarn guiding rod. Variable speed motors are each provided for the drive of the winding shaft and also for the traverse gearing. The variable speed motors are controlled by a controlling device, which presets wobble curves for each of the two variable speed motors in order to prevent patterning. By means of the wobble curves, the otherwise constant nominal speeds of the variable speed motors are periodically altered. The wobble curves of the two variable speed motors are synchronous with regard to their antipatterning periods, but in regard to their antipatterning disturbances (amplitudes) are contrasting, so that unacceptable thread tension can be avoided during wobbling. Preferably, it can be further provided that the antipatterning period and also the antipatterning disturbance can be varied by a preset mean value, whereby the antipatterning is even more effective.
It is an object of the present invention to improve the known device with regard to its drives and antipatterning.
This object has been achieved in accordance with the present invention in that a speed transmitter, arranged on a delivery shaft of the delivery device, transmits a delivery speed as the master speed to the control device, which in turn transmits the respective variable nominal speed to the speed regulators arranged at the variable speed motors, which nominal speeds arise from the override of the respective constant nominal speeds and the respective wobble curves.
In a further development of the above mentioned prior art, the control device of the present invention is thus not only coupled with the variable speed motors of the winding shaft and the traverse gearing, but also with a master shaft speed transmitter. If, for whatever reason, speed deviations occur at the master shaft, these will be transmitted directly by means of the speed transmitter to the control device, which can then adapt exactly the preset speeds for the winding shaft and the traverse gearing accordingly. In the control device, the values for the antipatterning disturbances (amplitudes) and the antipatterning periods of the wobble curves are also set, and these values are transmitted further as set to both the speed regulators, preferably frequency convertors.
If the device is applied in open-end spinning machines, then the delivery shaft is in this case a yarn withdrawal shaft, which, under the action of a pressure roller, withdraws the spun thread from the respective spinning rotor and feeds it to the bobbin. This withdrawal shaft can be coupled by means of a mechanical gearing directly with a draw-in shaft, by means of which the fiber material to be spun, for example a sliver, is fed. The withdrawal shaft can, as before, be electrically connected with the central drive motor of the individual spinning rotors.
The antipatterning period is frequently based not on the speed of the traverse gearing but rather on the double stroke of the traversing yarn guide. An advantageous antipatterning can be achieved when the antipatterning period amounts to 8 to 40 double strokes. As for the antipatterning disturbance, a variation of the speeds of between 1% to 15% has proven to be sufficient.
Other advantages, features, and details of the invention will be found in the description below in which a number of embodiments of the invention are described in detail with reference to the drawings. The features referred to in the claims and the specification may be important to the invention individually or in any combination.